/*	$Id$	*/
/*
 * Fowler/Noll/Vo hash code
 *
 * @(#) Revision: 1.8 $
 * @(#) Id: hash_32.c,v 1.8 2003/10/03 20:38:13 chongo Exp $
 * @(#) Source: /usr/local/src/cmd/fnv/RCS/hash_32.c,v $
 *
 *
 * The basis of this hash algorithm was taken from an idea sent
 * as reviewer comments to the IEEE POSIX P1003.2 committee by:
 *
 *	  Phong Vo (http://www.research.att.com/info/kpv/)
 *	  Glenn Fowler (http://www.research.att.com/~gsf/)
 *
 * In a subsequent ballot round:
 *
 *	  Landon Curt Noll (http://www.isthe.com/chongo/)
 *
 * improved on their algorithm.  Some people tried this hash
 * and found that it worked rather well.  In an EMail message
 * to Landon, they named it the ``Fowler/Noll/Vo'' or FNV hash.
 *
 * FNV hashes are designed to be fast while maintaining a low
 * collision rate. The FNV speed allows one to quickly hash lots
 * of data while maintaining a reasonable collision rate.  See:
 *
 *	  http://www.isthe.com/chongo/tech/comp/fnv/index.html
 *
 * for more details as well as other forms of the FNV hash.
 ***
 *
 * NOTE: The FNV-0 historic hash is not recommended.  One should use
 *	 the FNV-1 hash instead.
 *
 * To use the 32 bit FNV-0 historic hash, pass FNV0_32_INIT as the
 * uint32_t hashval argument to cnp_fnv32_hash().
 *
 * To use the recommended 32 bit FNV-1 hash, pass FNV1_32_INIT as the
 * uint32_t hashval argument to cnp_fnv32_hash().
 *
 ***
 *
 * Please do not copyright this code.  This code is in the public domain.
 *
 * LANDON CURT NOLL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
 * EVENT SHALL LANDON CURT NOLL BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 *
 * By:
 *	chongo <Landon Curt Noll> /\oo/\
 *	  http://www.isthe.com/chongo/
 *
 * Share and Enjoy!	:-)
 */

#include <sys/types.h>

#include <stdint.h>
#include <stdlib.h>

#include "fnv.h"


/*
 * 32 bit magic FNV-0 and FNV-1 prime
 */
#define FNV_32_PRIME ((uint32_t)0x01000193)

/*
 * 64 bit magic FNV-0 and FNV-1 prime
 */
#define FNV_64_PRIME ((uint64_t)0x100000001b3ULL)




/*
 * cnp_fnv32_hash()
 *
 * Perform a 32-bit Fowler/Noll/Vo hash on a buffer
 *
 * input:
 *	buf	- start of buffer to hash
 *	len	- length of buffer in octets
 *	hval	- previous hash value or 0 if first call
 *
 * returns:
 *	32 bit hash as a static hash type
 *
 * NOTE: To use the 32 bit FNV-0 historic hash, use FNV0_32_INIT as the hval
 *	 argument on the first call to cnp_fnv32_hash().
 *
 * NOTE: To use the recommended 32 bit FNV-1 hash, use FNV1_32_INIT as the hval
 *	 argument on the first call to cnp_fnv32_hash() or cnp_fnv32_str().
 */
uint32_t
cnp_fnv32_hash(const void *buf, size_t len, uint32_t hval)
{
	const uint8_t *bp = (const uint8_t *)buf;	/* start of buffer */
	const uint8_t *be = bp + len;		/* beyond end of buffer */

	/*
	 * FNV-1 hash each octet in the buffer
	 */
	while (bp < be) {

		/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
		hval *= FNV_32_PRIME;
#else
		hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif

		/* xor the bottom with the current octet */
		hval ^= (uint32_t)*bp++;
	}

	return (hval);
}

/*
 * cnp_fnv32a_buf - perform a 32 bit Fowler/Noll/Vo FNV-1a hash on a buffer
 *
 * input:
 *	buf	- start of buffer to hash
 *	len	- length of buffer in octets
 *	hval	- previous hash value or 0 if first call
 *
 * returns:
 *	32 bit hash as a static hash type
 *
 * NOTE: To use the recommended 32 bit FNV-1a hash, use FNV1_32A_INIT as the
 * 	 hval arg on the first call to cnp_fnv32a_hash().
 */
uint32_t
cnp_fnv32a_hash(const void *buf, size_t len, uint32_t hval)
{
	const uint8_t *bp = (const uint8_t *)buf;	/* start of buffer */
	const uint8_t *be = bp + len;		/* beyond end of buffer */

	/*
	 * FNV-1a hash each octet in the buffer
	 */
	while (bp < be) {

		/* xor the bottom with the current octet */
		hval ^= (uint32_t)*bp++;

		/* multiply by the 32 bit FNV magic prime mod 2^32 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
		hval *= FNV_32_PRIME;
#else
		hval += (hval<<1) + (hval<<4) + (hval<<7) + (hval<<8) + (hval<<24);
#endif
	}

	return (hval);
}

/*
 * cnp_fnv64_buf - perform a 64 bit Fowler/Noll/Vo hash on a buffer
 *
 * input:
 *	buf	- start of buffer to hash
 *	len	- length of buffer in octets
 *	hval	- previous hash value or 0 if first call
 *
 * returns:
 *	64 bit hash as a static hash type
 *
 * NOTE: To use the 64 bit FNV-0 historic hash, use FNV0_64_INIT as the hval
 *	 argument on the first call to cnp_fnv64_hash().
 *
 * NOTE: To use the recommended 64 bit FNV-1 hash, use FNV1_64_INIT as the hval
 *	 argument on the first call to cnp_fnv64_hash().
 */
uint64_t
cnp_fnv64_hash(const void *buf, size_t len, uint64_t hval)
{
	const uint8_t *bp = (const uint8_t *)buf;	/* start of buffer */
	const uint8_t *be = bp + len;		/* beyond end of buffer */

	/*
	 * FNV-1 hash each octet of the buffer
	 */
	while (bp < be) {

		/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
		hval *= FNV_64_PRIME;
#else
		hval += (hval << 1) + (hval << 4) + (hval << 5) +
			(hval << 7) + (hval << 8) + (hval << 40);
#endif

		/* xor the bottom with the current octet */
		hval ^= (uint64_t)*bp++;
	}

	return (hval);
}
/*
 * cnp_fnv64a_buf - perform a 64 bit Fowler/Noll/Vo FNV-1a hash on a buffer
 *
 * input:
 *	buf	- start of buffer to hash
 *	len	- length of buffer in octets
 *	hval	- previous hash value or 0 if first call
 *
 * returns:
 *	64 bit hash as a static hash type
 *
 * NOTE: To use the recommended 64 bit FNV-1a hash, use FNV1_64A_INIT as the
 * 	 hval arg on the first call to cnp_fnv64a_hash().
 */
uint64_t
cnp_fnv64a_hash(const void *buf, size_t len, uint64_t hval)
{
	const uint8_t *bp = (const uint8_t *)buf;  /* start of buffer */
	const uint8_t *be = bp + len;		   /* beyond end of buffer */

	/*
	 * FNV-1a hash each octet of the buffer
	 */
	while (bp < be) {

		/* xor the bottom with the current octet */
		hval ^= (uint64_t)*bp++;

		/* multiply by the 64 bit FNV magic prime mod 2^64 */
#if defined(NO_FNV_GCC_OPTIMIZATION)
		hval *= FNV_64_PRIME;
#else
		hval += (hval << 1) + (hval << 4) + (hval << 5) +
			(hval << 7) + (hval << 8) + (hval << 40);
#endif
	}

	return (hval);
}
